The Alcove (1985)

Storyline : An English soldier returns home from the Zulu war with the
daughter of a tribal king as his slave . The spoils of war, ya know? While
he's been gone, his wife has been having an affair with the female
housekeeper. Not at all pleased with being a slave, the Ebony princess notices the
mistress of the house engaging in a quick bit of foreplay with the
housekeeper and plots her revenge starting with the seduction of the
mistress.